To obtain pokémon missing from your version you need to trade with someone who has the opposite version.
Omega ruby legendary exclusives.
Pokemon omega ruby and alpha sapphire are enhanced remakes of the original pokemon ruby and sapphire which released on the game boy advance 11 years ago.
Omega ruby alpha sapphire each include pokémon that cannot be obtained in the alternate version.
As with all games pokémon omega ruby and pokémon alpha sapphire have a variety of pokémon that can only be obtained within one game.
This item is the clear bell in omega ruby and the tidal bell in alpha sapphire.
Interact with it and ho oh will appear in omega ruby and lugia will appear in alpha sapphire.
Pokemon omega ruby and alpha sapphire features a massive number of legendary pokemon some can be found in both versions and some are exclusive to a single version.
This causes a portal to appear.